To be different and mix things up, which isn't all the uncommon. Films change things from the source all the time and people don't freak out, the outrage is selective. I'd be fine with original Surfer as well.
Keeping original gender and/or race only matters when it's integral to the character's back story. Some matter more than others, some don't matter at all.
Surfer being male or female doesn't really change the character's story too much aside from aesthetics. Watch.
Norrin's Norra’s life changed forever when a menacing alien spacecraft pierced Zenn-La's long-neglected defense systems. Convincing a Council of Scientists member to provide him her with a spaceship, Radd soon confronted the invader, Galactus, who intended to consume Zenn-La. Radd offered to become his herald and seek out new worlds for him in exchange for Galactus sparing Zenn-La. Galactus agreed, transforming Radd into a silver-skinned, cosmic-powered super-being patterned after an adolescent fantasy plucked from Norrin's Norra’s memories. Known thereafter as the Silver Surfer because of the silvery flying board he she rode, Radd departed Zenn-La with Galactus. -Surfer's Origins